Abstract: Agricultural ecosystem is a kind of man-made ecosystem, which is set up on the basis of the natural ecosystem. Its function is to meet the needs of the people for various agricultural products. In order to get more agricultural products with better quality from agricultural ecosystem on the basis of beniga cycle, it is necessary to analyse and understand its special characteristics.Agricultural ecosystem has four outstanding characteristics,which are very different from common natural ecosystems. These characteristics are the increase in the input and output of materials and energy, large input of auxiliary energy, the tendency of shortening food chains, the tendency of extending the chains of utilizing survivals.